Problem with Keylight in Shake 4.1
by Peter Egermann
on
Oct 14, 2008 at 9:38:47 pm
hello,
i am not very experienced in keying but i used keylight several times and i was always satisfied with the results. today i got some test material shot with the sony ex1-camera in 1080p. i thought that it looked quite good but when trying to pull a key with keylight i got a result that i don't understand at all. it creates some kind of an edge. is there someone who knows why i am having those difficulties? is it something in the material i got? do you think that the lighting of the shot is okay?
in the keylight node i just selected the color of the greenscreen. i did not make any changes on the other settings. i tried the fine adjustment sliders, but they did not help.
here are the samples in jpeg (it's just the part of the image that makes trouble):
Re: Problem with Keylight in Shake 4.1 by Les Stuck on Oct 15, 2008 at 4:40:34 pm
It looks like the camera had a sharpening filter turned on.
Notice how there's a lot of contrast and an extra sharp edge
in the original file, makng the screen too bright in that area.
Hopefully you can go back and reshoot with
sharpening or detailing turned off.
Otherwise, you may just have to crank up Keylight's screenRange.
Re: Problem with Keylight in Shake 4.1 by Peter Egermann on Oct 15, 2008 at 5:53:53 pm
thank you very much for your help. we will have to check if there was a shapening filter turned on, that seems to be an explanation. today i went through andrew's tutorials, they were quite helpful (thanks a lot, andrew!).
i found out that keylight does a great job when using a replacement color which is as bright or brighter as the original greenscreen. when i want to use a darker background, keylight produces the edge-problem which i described. do you think that the greenscreen in the original footage is too bright? i thought that it may help to give a little less light to it.
Re: Problem with Keylight in Shake 4.1 by Andrew Shanks on Oct 16, 2008 at 9:44:16 pm
Hey Peter,
thanks for the kudos, ...wish I had time to redo those tutorials as I do things a little different now, but its still okay.
In regards to the footage, definitely looks like camera sharpening. Most digital video cameras by default have sharpening on (as thats how they get the great looking vivid sharp images that look good at demos ;-). In the EX it is called detailing I believe, so just turn that nasty pup off. The other issue with the EX, as has been stated, is the limited colour depth it has, comparable to DV, and it is also an MPEG2 long_GOP based format, similar but better system to HDV. More details here:
These all pose issues to your key. My suggestions for keys are to turn off detail on your EX camera (if you need sharpening, do it in post), if it has already been shot, you may need to choke in your matte edges (erode) to eliminate the edging (not a pretty solution granted). The other thing to do is to do the same colour bluring you would do for DV (as in the first tutorial I did). Your edges aren't going to be as good because of the format, but with some persistance hopefully you'll have passable results.
Re: Problem with Keylight in Shake 4.1 by Eric Meek on Oct 21, 2008 at 2:12:33 pm
sharpening can have an effect but it shouldnt mater with shake. There are techniques that will take care of that edge. Reshooting is very unnecessary. If your a good shake user you can kill that edge. by using multiple keys, dilate erodes, color space blur color space, etc. Dont think its not fixable cause it is very much so. Ive seen worse fixed.
